help my chickens are dying

I do not know what I have done wronge or what I can do to make it better but in the last 2 nights i have lost 3 chickens it has been -20c outside they are inside there coop is 10c there is 40 birds in there. I do not know what to do I got 40 1 to 2 year old chickens in may and I have lost 19 of them now!! please help me

Hon, we need a lot more info. How old are the birds, what kinds are they. Tell us about your coop, how large is it, how is it built, how much ventillation does it have. Okay, looked back and saw the age, so adult birds. Still need more info on the coop and how you're finding the birds.....any sign of predators? Just fell off the roost?

They are all found in the coop by the wall most times under the windows there is two windows open a bit and a small chicken size door for them to get in and out I al so have a man door that I go thru checking on them 2 times a day my coop is 8/16

Are they showing any signs of illness at all the day before? Puffed up, any respiratory sounds, not eating, do they show any sign of predator injury or pecking from other chickens? If there is absolutely no sign that you can pin point you may have to have a necropsy done on one if you want to figure out what's going on.

You might try treating the whole flock with a round of Corid. Have to start somewhere and with multiple, fast deaths with few symptoms I think that's where I'd start. Could also have a vet run a fecal sample for parasites.